Leadless chip socket

ABSTRACT

A chip carrier socket for solid state electronic chip carrier packaged elements made up of a hollow body having a cover, a hinged top on the body providing a space between the top and the body, a chip carrier to be placed in the space and serpentine shaped springs in the hollow body and extending upwardly therethrough to engage electronic metalized pad areas on said chip carrier package. The lower end of the springs being adapted to rest on a bottom closure, the lower ends of the springs extending out through the bottom closure and the upper end of the springs extending through the top of the body and being slidable relative thereto.

GENERAL DESCRIPTION OF THE INVENTION

The chip carrier disclosed herein is designed to accept leadless chipcarriers with thickness range from 0.050 inches to 0.100 inches and/orother packages with the differences in package thicknesses of 0.050inches. The sockets can be used for many applications including ambienttesting and high temperature "burn in" testing up to relatively hightemperatures i.e. 210° C.

The main advantage of the sockets disclosed herein is that they have aunique spring contact and plastic design which accurately locates theelectrical contact point relative to the termination pad on the chipcarrier.

The sockets disclosed herein are designed to accept molded pad leadlesschip carriers with relatively close center to center pad spacing. Thesockets will accept carriers capable of withstanding burn intemperatures up to 210° C.

The sockets which are available in gold plated beryllium copper or goldplated beryllium nickel are designed to generate a normal force of 50grams when a 0.075 inch thick leadless chip carrier is placed in thesocket. The contact is designed such that the normal force generated bya 0.050 inch thick leadless chip carrier is not significantly differentthan the normal force generated by a 0.100 inch thick leadless chipcarrier in the socket. Because of this the force required to close thesocket with a 0.050 inch thick leadless carrier in place is not muchdifferent than the force required to close the socket with a 0.100 inchleadless chip carrier in place.

The latching mechanism is formed from stainless steel to handle the hightemperatures of the environment it is used in. The latch is designed tobe easily operated with finger pressure.

When the cover on the socket is closed, the force the contacts exert onthe cover through the device keeps the latch in its closed position.

The socket is designed to accept leadless chip carriers on 0.050 inchcenters but the design is applicable to other centerlines on subsequentevolutions of the product.

Operation of the socket is very simple. First, the socket is opened bypulling back on the latch part 24 which allows the socket cover 13 to berotated to the open position to allow the leadless chip carrier 25 to beplaced in the socket. The locating bosses 30 on the body 11 provide alarge lead-in guide to assist in accurately locating the leadless chipcarrier 25 in the socket. With the leadless chip carrier in place asshown in FIG. 2, the socket cover 13 is swung to the closed position.The bosses 31' on the cover contact the top of the leadless chip carrier25 pushing the carrier down against the contacts. This force causes thecontacts to deflect the amount required by the thickness of the leadlesschip carrier. When the rotation of the socket cover 13 reaches the fullyclosed position, the latch 24 snaps into the closed position holding thecover closed and the leadless chip carrier in place.

The entire socket assembly is designed to have a continuous use maximumtemperature of 210° C. The plastic parts of the socket are molded fromglass reinforced polyphenylene sulfide. The contacts are available ineither gold-plated beryllium copper (for use up to 175° C. orgold-plated beryllium nickel (for use up to 210° C.). The latchingmechanism is constructed of stainless steel to withstand hightemperature exposure. The socket assembly is constructed from severalparts. These parts are the latch part 24, the socket cover part 13, thesocket body part 11, device locating bosses 30, (located on the socketbody part 11) springs 19 having contact ends 27 and 20 and the bottomclosure 12.

The contact springs 19 are mechanically and electrically isolated fromeach other in the socket body and are held captive in the body 11 whichis ultrasonically welded to the bottom closure 12. The socket cover 13is assembled to the socket body 11 by a snap fit. The latch 24 snapsinto the socket cover 13 to complete the assembly.

REFERENCE TO PRIOR ART

Applicant knows of no relevant prior art to the above disclosure.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a socket series having theability to handle a wide range of leadless chip carriers with varyingdimensions.

Another object of the invention is to provide a leadless chip carrierwith a contact normal force which is uniform over a wide deflectionrange.

Another object of the invention is to provide a socket that utilizes aself-engaging latching mechanism.

Another object of the invention is to provide an overall size of socketwhich is much smaller than comparable designs.

Another object of the invention is to provide a unique design of socketwhich accurately locates the electrical contact point relative to theterminal pad on the chip carrier.

Another object is to provide a socket with a normal force which isfairly constant on a chip carrier over a wide deflection range.

Another object of the invention is to provide a contact that has a largerange of deflection.

Another object is to provide a contact which is much smaller thanconventional cantilever type contacts.

Another object of the invention is to provide a contact having the abovefeatures with a contact surface which is rounded so as not to gall thepoint of contact on the leadless chip carriers.

Another object of the invention is to provide a one piece, easy tooperate latching mechanism.

Another object is to provide a normally closed type of latch.

Another object of the invention is to provide a latch that when placedunder load, may be opened easily with finger pressure.

With the above and other objects in view, the present invention consistsof the combination and arrangement of parts hereinafter more fullydescribed, illustrated in the accompanying drawing and more particularlypointed out in the appended claims, it being understood that changes maybe made in the form, size, proportions and minor details of constructionwithout departing from the spirit or sacrificing any of the advantagesof the invention.

GENERAL DESCRIPTION OF THE DRAWINGS

FIG. 1 is a isometric view of the chip carrier body according to theinvention without the socket cover and a chip carrier in place.

FIG. 2 is a longitudinal cross sectional view taken on line 2--2 of thebody of FIG. 1 showing a cover and chip carrier in place.

FIG. 3 is an isometric view of the chip carrier, the chip carrier is apackage style used by Semiconductor Manufacturers to house theirintegrated circuit designs. The invention is meant to provide anelectrical connection to the chip carrier.

FIG. 4 is an integrated side view of the spring contact.

DETAILED DESCRIPTION OF THE DRAWINGS

Now with more particular reference to the drawings. A chip carriersocket is shown comprising a hollow body 11, the bottom having a bottomclosure 12 and a top closure 14 defining a hollow space therebetween, acover 13 is swingably attached to the body at pivot 22 and bosses 37'and swingable from an open position to the closed position showndefining a space between the top closure 14 and the cover 13. A chipcarrier 25 which is normally square in shape (but not restricted to thatshape) and has a plurality of metalized pads to which contact arms 26are connected, is supported on the upper end of the contacts 20 with onecontact engaging each metalized pad. The body has a substantially flatoutside top surface 37 and a substantially flat outside bottom surface38. A substantially flat inside bottom surface 39, with flat sides. Thebody 11 has a hollow 42 inside defined by the relatively flat insidebottom surface 39 and a relatively flat inside top surface 40. Thebottom 12 has spaced openings 21 and 41 and openings 18 extend throughthe top 14 from hollow 42 to the outside. A plurality of springs 19,each made of a continuous piece of material of generally uniform crosssection, having accordion pleated sections 28 between the upper ends 20and the lower ends 27'. Upper straight ends 20 extend through openings18 in the top 14 and the lower straight ends 27' extend through openings41 and 21 in the bottom 12. Each spring 19 has a lower end convolutionthat rests on bottom 12. The upper contact members 20 extend through theholes 18 and terminate a substantial distance above the top surface 37.The cover 13 has a flat bottom surface which rests on the bosses 30 andthe flange 43 which is attached to the cover 13 rests on the boss 29.The spring latch 24 which is supported on the flange 43 in a mannerfamiliar to those skilled in the art has an end 32' which underlies theboss 29 on the body when the cover is in the closed position as shown inFIG. 2. Springs having an intermediate accordion pleated part made offour convolutions generally accordion pleated in shape. Pleats havegenerally straight intermediate parts and straight upper contact ends 20that extend through the holes 18, which have tapered recesses 15, in thetop 14. Lower ends 27' of the springs extend through holes 21 in bottom12 and may connect to a suitable conductor. Springs 19 are supported inthe space between the boss 17 and the inside of the inside of the hollowbody. The boss 17 is part of the top 14. The upper end of the contacts20 project through and are slideably received in holes 18. Each of thecontact springs 19 are formed of an electronically conductive materialsuch as beryllium copper which may be gold plated. The upper end of thecontacts 20 extend through holes in top 14 and slide up and down whenthe springs 19 are compressed by the chip carrier 25 when the cover 13is closed.

The latch means 24 is adapted to hold the cover in closed position. Thelatch may be attached to cover 13 in a suitable manner familiar to thoseskilled in the art. When the cover engages the socket body as said coverswings to the closed position deflecting the convoluted springs whichexert an even force on the contact. The end 32' underlies the boss 29holding the cover 13 in position. The convolutions of the springs aregenerally sinusoidal in shape and formed into accordian shaped pleats,that is, the ends of the convolutions are curved and the parts betweenthe ends are straight so that when compressed by a force on the upperends 20 of the contacts and on the lower convolutions 27 will cause theintermediate parts of the spring 19 to act in a cantilever fashion. Itwill be noted that the amplitude of the convolutions on the upper end ofthe spring are less than the amplitude of the lower convolutionsresulting in a more uniform spring action. Likewise, the inner crests ofthe springs rest against the boss 17 and the lower convolutions 27 reston the bottom cover 12 while the lower contact ends 27' are bent atright angles to the lower convolution and through spaced openings 21 inthe bottom cover 12.

The body 11 has spaced upwardly extending bosses 30 and 30' that engagethe underside of the cover 13 when in close position thereby limitingthe downward swinging movement of the cover and the cover has downwardlyextending bosses 31' thereon which engage the upper side of the chipcarrier 25 thereby holding it down against the tension of the springs19.

The ends of the contacts 27' and the ends of the contacts 20 are bentback on themselves providing a smooth surface to prevent galling. Thesocket cover 13 is rotated to the open position to allow the leadlesschip carrier 25 to be placed in the socket. The locating bosses 30' onthe body 11 have large lead in area to assist in accurately locating thechip carrier 25 in the socket. With the leadless chip carrier 25 inplace the socket cover 13 is swung to close position. The bosses 31' onthe cover 13 contact the top of the leadless chip carrier 25 pushing thecarrier down against the contacts ends 20. Boss 17 has a recess on itslower end which receives an end of the lowermost convolution 27 of eachspring contact. This force causes the contacts 19 to deflect the amountrequired by the thickness of the leadless chip carrier. When the coverreaches it fully closed position, the latch 24 snaps into the closedposition holding the cover closed and the leadless chip carrier inplace.

The foregoing specification sets forth the invention in its preferred,practical forms but the structure shown is capable of modificationwithin a range of equivalents without departing from the invention whichis to be understood is broadly novel as is commensurate with theappended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A leadless chip socketcomprising,a body having a hollow therein, said body having a top havinga substantially flat outside top surface, a bottom having asubstantially flat bottom surface and sides, said hollow in said bodybeing defined by a relatively flat inside bottom surface and arelatively flat inside top surface, spaced first openings extendingthrough said top from said hollow to the outside of said body, spacedsecond openings in said bottom and extending from said hollow to theoutside of said body, a plurality of accordion pleated springs in saidhollow, each said spring being made up of a continuous piece of materialof generally uniform cross section, each said piece of material havingan intermediate accordion pleated portion and a straight upper endcontact member and a straight lower end contact member, each said uppercontact member extending upwardly through a said first opening asubstantial distance, said lower contact members extending through saidsecond openings in said bottom a substantial distance, a cover having agenerally flat bottom surface, means supporting said cover on said bodywith a space therebetween for receiving a plate-like chip carrier withsaid upper contact members engaging the lower side of said chip carrier,thereby deflecting said accordion pleated portion of said springswhereby generally uniform force is exerted on said chip carrier, saidcover being adapted to swing to an open position with said covergenerally perpendicular to said outside top surface whereby a chipcarrier can be removed from said space, latch means on said cover forholding said cover in closed position with a chip carrier in said space.2. The socket recited in claim 1 wherein said springs are made ofrelatively thin flat material.
 3. The socket recited in claim 1 whereinsaid body has spaced upwardly extending bosses thereon for engaging saidchip carrier and accurately locating said chip carrier relative to saidsocket.
 4. The leadless chip socket recited in claim 1 wherein some ofsaid springs each have an end convolution resting on said bottom.
 5. Theleadless chip socket recited in claim 4 wherein said upper end contactmembers are moveable a substantial distance towards said top of saidbody.